The differences I've seen between "raid edition" drives and regular drives are:
* Dramatically better vibration resistance. If you are going to bolt a drive
or two into a desktop it doesn't matter so much. If you are going to plug
a drive into a 16 bay enclosure or even into a 1U node with a ton of fast
fans you might well see a large performance difference because of the
vibration. The specification sheets do reflect this btw, I assume this
is mostly lower density platters and stronger motors for positioning
the heads. This is especially noticeable on the consumer drives with the
higher density platters (375-500GB per platters). I've seen consumer
drives that manage 120MB/sec drop to a noisy fluctuation between 18-30
MB/sec because of vibration
* Consumer drives (at least the non-media ones) often have occasional
thermal recalibrations. This seems better these days, but last thing
you want is a recal triggering a degraded array.
* Consumer drives will go to heroic efforts to read a bad sector, exactly
the opposite of what you want in a RAID drive. In a RAID it's better to
fail and yell bloody murder... especially when the rereading a sector
a bunch causes the raid to time out and drop the disk.
Of course manufactures claim various things about error rates per billion
bits, designed duty cycles (40 hours a week vs 24/7), improve temperature
envelops, and related. Alas while this is nice to hear I've not seen any
direct results because of it.
As an example, 500GB wd caviar $64.99, 500GB WD RE3 $89.99. IMO if you are
building a raid or heavily used 1U with a ton of fans the extra $25 is worth it.